Dermatological use of nanoparticles has shown promise for the delivery of drugs and other therapeutic agents for both medical and cosmetic purposes (Nohynek et al. (2008) Skin Pharmacol. Physiol., 21:136-149). There has already been successful commercialization of nanoparticle-based products in the dermatological field, including sunscreen formulations and vitamin A products (Prow et al. (2011) Adv. Drug Deliv. Rev., 63: 470-491). Various therapeutic and cosmetic applications of nanoparticles have been described as well as the need for developing a method that can determine penetration of nanoparticles through skin layers (DeLouise, L. A. (2012) J. Investig. Dermatol., 132:964-975). Most applications of nanoparticle-based delivery systems in the dermatological field to date have been for treating skin cancer, wound healing, and delivery of antimicrobial agents (Prow et al. (2011) Adv. Drug Deliv. Rev., 63: 470-491; DeLouise, L. A. (2012) J. Investig. Dermatol., 132:964-975). In addition, nanoparticles can be applied topically for systemic delivery of drugs, such as Estrasorb®, a commercial formulation that uses topical application of an emulsion for systemic delivery of estradiol (Lee et al., Micellar nanoparticles: Applications for topical and passive transdermal drug delivery. In Handbook of Non-Invasive Drug Delivery Systems; Kulkarni, V. S., Ed.; Elsevier, Inc.: Amsterdam, Netherlands, 2010; pp. 37-58). Titanium dioxide and zinc oxide nanoparticles are also commonly used in sunscreen products to protect the skin from sun's ultraviolet (UV) radiation, which is considered to be the main cause of skin cancer (Smijs et al. (2011) Nanotechnol. Sci. Appl., 4:95-112).
Ultraviolet (UV) irradiation from the sun, the primary cause of most skin cancer, results in oxidative stress that can overwhelm the skin's natural antioxidant defense mechanisms, leading to significant reactive oxygen species (ROS) generation. ROS cause DNA damage that can result in gene mutations and also indirectly activate oncogenic signaling pathways. Sunscreens and skincare products commonly employed for sun protection are inadequate because they break down when exposed to UV radiation, need frequent reapplication and are particularly poor at blocking the long wavelength UVA that produces much of the ROS. In addition, topical antioxidants that are currently available commercially have poor stability after application and following UV exposure and do not penetrate the skin to reach the cells that are at risk for oncogenic transformation. The rate of cutaneous squamous cell carcinoma (SCC) has been rapidly rising due to increased exposure to ultraviolet (UV) radiation, the primary cause of skin cancer (Karia et al. (2013) J. Am. Acad. Dermatol., 68:957-966). Delivery of antioxidants in active form through skin layers and maintaining their protective effect has been challenging because of their limited stability and permeability through skin layers. Thus, there remains a strong need to develop applications designed to deliver nanoparticles and the drugs incorporated in them past the skin's outer surface into deeper tissues (DeLouise, L. A. (2012) J. Investig. Dermatol., 132:964-975; Zhang et al. (2010) Int. J. Pharm., 402:205-212) to sustain the effect of the treatment. Effective delivery of biological agents to deep layers of the skin and maintaining their activity for a sustained period that could play a protective role and facilitate skin repair/regeneration remains a challenge. Indeed, there is no such skin care product currently available in the market that contains biologically active molecules in a nanoparticle formulation (Halliday et al. (2012) J. Invest. Dermatol., 132(2):265-267; Panyam et al. (2003) Adv. Drug Deliv. Rev., 55(3):329-347).